Regardless
of which type of alternate air source you select, remember that its performance
will depend on the ability of the regulator first stage to deliver air, particularly
when it is supplying two second stages and a power inflator. The bottom lines:
Given the type of diving you plan to do, how will it work for you in a worst-case
scenario? How much risk are you willing to accept? If you dive solo, under demanding
conditions or in overhead environments, the greater your need for a completely
independent air source and a high-performance regulator as your alternate air
source.
(Excerpt used from New Diver Magazine)